Oppel's main conclusions were as follows:—"There are found in the developmental stages of different Vertebrates 'similar ontogenetic series,' that is to say, Vertebrates show at definite stages similarities with one another in the degree of development of the different organs. Early stages resemble one another, so also do later stages; equivalent stages of closely allied species resemble one another, and older stages of lower animals resemble younger stages of higher animals; young stages are more alike than old stages.... The differences which these similar series show (for which reason they cannot be regarded as identical) may be designated as temporal disturbances in the degree of development of the separate organs or organ-systems. Some organs show very considerable temporal dislocations, others a moderate amount, others again an inconsiderable amount. Among the developmental stages of various higher animals can be found some which correspond to the ancestral forms and also to the lower types which resemble these ancestral forms. On the basis of the tabulated data here given there can be distinguished with certainty in the ontogeny of Amniotes a pro-fish stage, a fish-stage, a land-animal stage, a pro-amniote stage, and following on these a fully developed reptile, bird or mammal stage."[529]

Oppel's methods were employed by Keibel[530] in his investigations on the development of the pig, which formed the model for the well-known series of Normentafeln of the ontogeny of Vertebrates which were issued in later years under Keibel's editorship. Keibel was more critical of the biogenetic law than Oppel, and he held that the ancestral stages distinguished by Oppel could not be satisfactorily established. He suggested an interesting explanation of heterochrony in development, according to which the premature or retarded appearance of organs in ontogeny stands in close relation with the time of their entering upon functional activity. Thus in many mammals the mesodermal part of the allantois often appears long before the endodermal part, though this is phylogenetically older. This Keibel ascribes to the fact that the endodermal part is almost functionless. "One can directly affirm," he writes, "that the time of appearance of an organ depends in an eminent degree upon the time when it has to enter upon functional activity. This moment is naturally dependent upon the external conditions. Among the highest Vertebrates, the mammals, the traces of phylogeny shown in ontogeny are to a great extent obliterated through the adaptation of ontogeny to the external conditions, and through the modifications which the germs of more highly organised animals necessarily exhibit from the very beginning as compared with germs which do not reach such a high level of development" (p. 754, 1897).

Study of individual variation in the time of appearance of the organs in embryos of the same species was prosecuted with interesting results by Bonnet,[531] Mehnert,[532] and Fischel.[533] Fischel found that variability was greatest among the younger embryos, and became progressively less in later stages. Like von Baer (supra, p. 114) he inferred that regulatory processes were at work during development which brought divergent organs back to the normal and enabled them to play their part as correlated members of a functional whole.

Important theoretical views were developed by Mehnert[534] in a series of publications appearing from 1891 to 1898. Like Keibel, Mehnert emphasised the importance of function in determining the late or early appearance of organs, but he conceived the influence of function to be exerted not only in ontogeny, but also throughout the whole course of phylogeny, by reason of the transmission to descendants of the effects of functioning in the individual life.

In his paper of 1897 Mehnert details the results of an extensive examination of the development of the extremities throughout the Amniote series. He finds that in all cases a pentadactylate rudiment is formed, even in those forms in which only a few of the elements of the hand or foot come to full development. But whereas in forms with a normally developed hand, e.g. the tortoise and man, all the digits develop and differentiate at about the same rate, in forms which have in the adult reduced digits, e.g. the ostrich and the pig, these vestigial digits undergo a very slow and incomplete differentiation, while the others develop rapidly and completely. He draws a general distinction between organs that are phylogenetically progressive and such as are phylogenetically regressive, and seeks to prove that progressive organs show an ontogenetic acceleration and regressive organs a retardation.[535] The acceleration or retardation affects not only the mass-growth of the organs, but also their histological differentiation.

Now between progression and functioning and between regression and functional atrophy there is obviously a close connection. Loss of function is well known to be one of the chief causes of the degeneration of organs in the individual life, and on the other hand, as Roux has pointed out, all post-embryonic development is ruled and guided by functioning. It is thus in the long run functioning that brings about phylogenetic progression, absence of functional activity that causes phylogenetic regression. This comes about through the transmission of acquired functional characters, a transmission which Mehnert conceives to be extraordinarily accurate and complete.

In general Mehnert adopts the functional standpoint of Cuvier, von Baer, and Roux. His considered judgment as to the phylogenetic value of the biogenetic law closely resembles that formed by von Baer, for he admits recapitulation only as regards the single organs, not as regards the organism as a whole. He has, however, much more sympathy with the law than either Keibel or Oppel, though he agrees that it cannot be used for the construction of ancestral trees. But he ascribes to it as a fact of development considerable importance. The following passage gives a good summary of his view as to the scope and validity of the law. "The biogenetic law has not been shaken by the attacks of its opponents. The assertion is still true that individual organogenesis is exclusively dependent on phylogeny. But we must not expect to find that all the stages in the development of the separate organs, which coexisted in any member of the phylogenetic series, appear at the same time in the individual ontogeny of the descendants, because each organ possesses its own specific rate of development. In this way it comes about naturally that organs which become differentiated rapidly, as, for example, the medullary tube, as a rule dominate earlier periods of ontogeny than do the organs of locomotion. For the same reason the cerebral hemispheres of man are almost as large in youth as in maturity. The picture which an embryo gives is not a repetition in detail of one and the same phylogenetic stage; it consists rather of an assemblage of organs, some of which are at a phyletically early stage of development, while others are at a phyletically older stage."[536]

A different line of attack was that adopted by O. Hertwig in a series of papers, which contain also what is perhaps the best critical estimate of the present position and value of descriptive morphology.[537]

It had not escaped the notice of many previous observers that quite early embryos not infrequently show specific characters even before the characters proper to their class, order and genus are developed—in direct contradiction of the law of von Baer. Thus L. Agassiz[538] had remarked in 1859 that specific characteristics were often developed precociously. "The Snapping Turtle, for instance, exhibits its small crosslike sternum, its long tail, its ferocious habits, even before it leaves the egg, before it breathes through lungs, before its derm is ossified to form a bony shield, etc.; nay, it snaps with its gaping jaws at anything brought near, when it is still surrounded by its amnion and allantois, and its yolk still exceeds in bulk its whole body" (p. 269).

Wilhelm His,[539] in the course of an acute and damaging criticism of the biogenetic law as enunciated by Haeckel, showed clearly that by careful examination the very earliest embryos of a whole series of Vertebrates could be distinguished with certainty from one another. "An identity in external form of different animal embryos, despite the common affirmation to the contrary, does not exist. Even at early stages in their development embryos possess the characters of their class and order, nay, we can hardly doubt, of their species and sex, and even their individual characteristics" (201).

This specificity of embryos was affirmed with even greater confidence by Sedgwick in a paper critical of von Baer's law.[540] He wrote:—"If v. Baer's law has any meaning at all, surely it must imply that animals so closely allied as the fowl and duck would be indistinguishable in the early stages of development; and that in two species so closely similar that I was long in doubt whether they were distinct species, viz., Peripatus capensis and Balfouri, it would be useless to look for embryonic differences; yet I can distinguish a fowl and a duck embryo on the second day by the inspection of a single transverse section through the trunk, and it was the embryonic differences between the Peripatuses which led me to establish without hesitation the two separate species.... I need only say ... that a species is distinct and distinguishable from its allies from the very earliest stages all through the development, although these embryonic differences do not necessarily implicate the same organs as do the adult differences" (p. 39).

Hertwig interprets this fact of the specific distinctness of closely allied embryos in the light of the preformistic conception of heredity. According to this view the whole adult organisation is represented in the structure of the germ-plasm contained in the fertilised ovum, from which it follows that the ova of two different species, and also their embryos at every stage of development, must be as distinct from one another as are the adults themselves, even though the differences may not be so obvious. If this be the case there can be no real recapitulation in ontogeny of the phylogeny of the race, for the egg-cell represents not the first term in phylogeny, but the last. The egg-cell is the organism in an undeveloped state; it has a vastly more complicated structure than was possessed by the primordial cell from which its race has sprung, and it can in no way be considered the equivalent of this ancestral cell.

Hertwig puts this vividly when he says that "the hen's egg is no more the equivalent of the first link in the phylogenetic chain than is the hen itself" (p. 160, 1906, b).

If ontogeny is not a recapitulation of phylogeny, how is it that the early embryonic stages are so alike, even in animals of widely different organisation? Hertwig's answer to this is very interesting. He takes the view that many of the processes characterising early embryonic development are the means necessarily adopted for attaining certain ends. Such are the processes of segmentation, the formation of a blastula, of cell-layers, of medullary folds where the nervous system is a closed tube, the formation of the notochord as a necessary condition of the development of the vertebral column, and so on. "Looked at from this standpoint it cannot surprise us that in all animal phyla the earliest embryonic processes take place in similar fashion, so that we observe the occurrence both in Vertebrates and Invertebrates of a segmentation-process, a morula-stage, a blastula and a gastrula. If now these developmental processes do not depend on chance, but, on the contrary, are rooted in the nature of the animal cell itself, we have no reason for inferring from the recurrence of a similar segmentation-process, morula, blastula, and gastrula in all classes of the animal kingdom the common descent of all animals from one blastula-like or gastrula-like ancestral form. We recognise rather in the successive early stages of animal development only the manifestation of special laws, by which the shaping of animal forms (as distinct from plant forms) is brought about" (p. 178, 1906, b).

"The principal reason why certain stages recur in ontogeny with such constancy and always in essentially the same manner is that they provide under all circumstances the necessary pre-conditions through which alone the later and higher stages of ontogeny can be realised. The unicellular organism can by its very nature transform itself into a multicellular organism only by the method of cell-division. Hence, in all Metazoa, ontogeny must start with a segmentation-process, and a similar statement could be made with regard to all the later stages" (p. 57, 1906, a).

Similarities in early development are therefore no evidence of common descent, and in the same way the resemblances of adult animals, subsumed under the concepts of homology and the unity of plan, are not necessarily due to community of descent, but may also be brought about by the similarity or identity of the laws which govern the evolution of these animals. In the absence, therefore, of positive evidence as to the actual lines of descent (to be obtained only from palaeontology), homological resemblance cannot be taken as proof of blood relationship, for homology is a wider concept than homogeny. The only valid definition of homology is that adopted in pre-evolutionary days, when those organs were considered homologous "which agree up to a certain point in structure and composition, in position, arrangement, and relation to the neighbouring organs, and accordingly possess identical functions and uses in the organism" (p. 151, 1906, b).

The concept of homology has thus a value quite independent of any evolutionary interpretation which may be superadded to it. "Homology is a mental concept obtained by comparison, which under all circumstances retains its validity, whether the homology finds its explanation in common descent or in the common laws that rule organic development" (p. 151, 1906, b). As A. Braun long ago pointed out, "It is not descent which decides in matters of morphology, but, on the contrary, morphology which has to decide as to the possibility of descent."[541]

Hertwig, in a word, reverts to the pre-evolutionary conception of homology. "We see in homology," he writes, "only the expression of regularities (Gesetzmaessigkeiten) in the organisation of the animals showing it, and we regard the question, how far this homology can be explained by common descent and how far by other principles, as for the present an open one, requiring for its solution investigations specially directed towards its elucidation" (p. 179, 1906, b).

Holding, as he does, that no definite conclusions can be drawn from the facts of comparative anatomy and embryology as to the probable lines of descent of the animal kingdom, Hertwig accords very little value to phylogenetic speculation. It is, he admits, quite probable that the archetype of a class represents in a general sort of way the ancestral form, but this does not, in his opinion, justify us in assuming that such generalised types ever existed and gave origin to the present-day forms. "It is not legitimate to picture to ourselves the ancestral forms of the more highly organised animals in the guise of the lower animals of the present day—and that is just what we do when we speak of Proselachia, Proamphibia and Proreptilia" (p. 155, 1906, b).

He rejects on the same general grounds the evolutionary dogma of monophyletic or almost monophyletic descent, and admits with Koelliker, von Baer, Wigand, Naegeli and others that evolution may quite well have started many times and from many different primordial cells.

There is indeed a great similarity between the views developed by O. Hertwig and those held by the older critics of Darwinism—von Baer, Koelliker, Wigand, E. von Hartmann and others. It is true the philosophical standpoint is on the whole different, for while many of that older generation were vitalists Hertwig belongs to the mechanistic school.

But both Hertwig and the older school agree in pointing out the petitio principii involved in the assumption that the archetype represents the ancestral form; both reject the simplicist conception of a monophyletic evolution (which may be likened to the "one animal" idea of the transcendentalists); both admit the possibility that evolution has taken place along many separate and parallel lines, and explain the correspondences shown by these separate lines by the similarity of the intrinsic laws of evolution; finally, both emphasise the fact that we know nothing of the actual course of evolution save the few indications that are furnished by palaeontology, and both insist upon the unique importance of the palaeontological evidence.[542]

It was a curious but very typical characteristic of evolutionary morphology that its devotees paid very little attention to the positive evidence accumulated by the palaeontologists,[543] but shut themselves up in their tower of ivory and went on with their work of constructing ideal genealogies. It was perhaps fortunate for their peace of mind that they knew little of the advances made by palaeontology, for the evidence acquired through the study of fossil remains was distinctly unfavourable to the pretty schemes they evolved.

As Neumayr, Zittel, Deperet, Steinmann and others have pointed out, the palaeontological record gives remarkably little support to the ideal genealogies worked out by morphologists. There is, for instance, a striking absence of transition forms between the great classificatory groups. A few types are known which go a little way towards bridging over the gaps—the famous Archaeopteryx, for example—but these do not always represent the actual phylogenetic links. There is an almost complete absence of the archetypal ancestral forms which are postulated by evolutionary morphology. Amphibia do not demonstrably evolve from an archetypal Proamphibian, nor do mammals derive from a single generalised Promammalian type. Few of the hypothetical ancestral types imagined by Haeckel have ever been found as fossils. The great classificatory groups are almost as distinct in early fossiliferous strata as they are at the present day. As Deperet says in his admirable book,[544] in the course of a presentation of the matured views of the great Karl von Zittel, "We cannot forget that there exist a vast number of organisms which are not connected by any intermediate links, and that the relations between the great divisions of the animal and vegetable kingdoms are much less close than the theory [of evolution] demands. Even the Archaeopteryx, the discovery of which made so much stir and appeared to establish a genetic relation between classes so distinct as Birds and Reptiles, fills up the gap only imperfectly, and does not indicate the point of bifurcation of these two classes. Intermediate links are lacking between Amphibia and Reptiles. Mammals, too, occupy an isolated position, and no zoologist can deny that they are clearly demarcated from other Vertebrates; indeed, no fossil mammal is certainly known which comes nearer to the lower Vertebrates than does Ornithorhynchus at the present day" (p. 115).

To take a parallel from the Invertebrata, B. B. Woodward,[545] after discussing the phylogeny of the Mollusca as worked out by the morphologists and comparing it with the probable actual course of the evolution of the group, as evidenced by fossil shells, sums up as follows:—"The lacunae in our knowledge of the interrelationships of the members of the various families and orders of Mollusca are slight however, compared with the blank caused by the total absence from palaeontological history of any hint of passage forms between the classes themselves, or between the Mollusca and their nearest allies. Nor is this hiatus confined to the Molluscan phylum; it is the same for all branches of the animal kingdom. There is circumstantial evidence that transitional forms must have existed, but of actual proof none whatever. All the classes of Mollusca appear fully fledged, as it were. No form has as yet been discovered of which it could be said that it in any way approached the hypothecated prorhipidoglossate mollusc, still less one linking all the classes" (p. 79).

Pointing in the same direction as the absence of transitional forms is the undeniable fact that all the great groups of animals appear with all their typical characters at a very early geological epoch. Thus, in the Silurian age a very rich fauna has already developed, and representatives are found of all the main Invertebrate groups—sponges, corals, hydroid colonies, five types of Echinoderms, Bryozoa, Brachiopods, Worms, many types of Mollusca and Arthropoda. Of Vertebrates, at least two types of fish are present—Ganoids and Elasmobranchs. In the very earliest fossiliferous rocks of all, the Precambrian formation, there are remains of Molluscs, Trilobites and Gigantostraca, similar to those which flourished in Cambrian and Silurian times.

The contributions of palaeontology to the solution of the problems of descent posed by morphology are, however, not all of this negative character. The law of recapitulation is in some well-controlled cases triumphantly vindicated by palaeontology. Thus Hyatt and others found that in Ammonites the first formed coils of the shell often reproduce the characters belonging to types known to be ancestral, and what is more they have demonstrated the actual occurrence of the phenomenon known as acceleration or tachygenesis, often postulated by speculative morphologists.[546] This is the tendency universally shown by embryos to reproduce the characters of their ancestors at earlier and earlier stages in their development.

The most valuable contribution made by palaeontologists to morphology and to the theory of evolution arose out of the careful and methodical study of the actual succession of fossil forms as exemplified in limited but richly represented groups. Classical examples were the researches of Hilgendorf[547] on the evolution of Planorbis multiformis in the lacustrine deposits of Steinheim, those of Waagen[548] on the phylogeny of Ammonites subradiatus, and the work of Neumayr and Paul[549] on Paludina (Vivipara).

These investigations demonstrated that it was possible to follow out step by step in superjacent strata the actual evolution of fossil species and to establish the actual "phyletic series."

To take an example from among the Vertebrates, Deperet has shown (loc. cit., pp. 184-9), that the European Proboscidea, belonging to the three different types of the Elephants, Mastodons and Dinotheria, have evolved since the Oligocene epoch along five distinct but continuous lines. The Dinotherian stock is represented at the beginning of the Miocene by the relatively small form D. cuvieri; this changes progressively throughout Miocene times into D. laevius, D. giganteum, and D. gigantissimum. Among the Mastodons two quite distinct phyletic series can be distinguished, the first commencing with Palaeomastodon beadnelli of the Oligocene, and evolving between the Miocene and Pliocene into Mastodon arvernensis, after traversing the forms M. angustidens and M. longirostris, the second starting with the M. turicensis of the Lower Miocene and evolving through M. borsoni into the M. americanus of the Quaternary. The phyletic series of the true elephants in Europe are relatively short, and go back only to the Quaternary, Elephas antiquus giving origin to the Indian elephant, E. priscus to the African.

The careful study of phyletic series brought to light the significant fact that these lines of filiation tend to run for long stretches of time parallel to, and distinct from one another, without connecting forms. This is clearly exemplified in the case of the Proboscidea, and many other examples could be quoted. Almost all rich genera are polyphyletic in the sense that their component species evolve along separate and parallel lines of descent.[550] "Such great genera as the genus Hoplites among the Ammonites, the genus Cerithium among the Gastropoda, the genus Pecten or the genus Trigonia among the Lamellibranchs, each comprise perhaps more than twenty independent phyletic series" (Deperet, p. 200).

Variation along the phyletic lines is gradual[551] and determinate, and appears to obey definite laws. The earliest members of a phyletic series are usually small in size and undifferentiated in structure, while the later members show a progressive increase in size and complexity. Rapid extinction often supervenes soon after the line has reached the maximum of its differentiation.

The general picture which palaeontology gives us of the evolution of the animal kingdom is accordingly that of an immense number of phyletic lines which evolve parallel to one another, and without coalescing, throughout longer or shorter periods of geological times. "Each of these lines culminates sooner or later in mutations of great size and highly specialised characters, which become extinct and leave no descendants. When one line disappears by extinction it hands the torch, so to speak, to another line which has hitherto evolved more slowly, and this line in its turn traverses the phases of maturity and old age which lead it inevitably to its doom. The species and genera of the present day belong to lines that have not reached the senile phase; but it may be surmised that some of them, e.g. elephants, whales, and ostriches, are approaching this final phase of their existence" (Deperet, p. 249).

It is one of the paradoxes of biological history that the palaeontologists have always laid more stress upon the functional side of living things than the morphologists, and have, as a consequence, shown much more sympathy for the Lamarckian theory of evolution. The American palaeontologists in particular—Cope, Hyatt, Ryder, Dall, Packard, Osborn—have worked out a complete neo-Lamarckian theory based upon the fossil record.

The functional point of view was well to the fore in the works of those great palaeontologists, L. Ruetimeyer (1825-1895) and V. O. Kowalevsky (1842-83), who seem to have carried on the splendid tradition of Cuvier. Speaking of Kowalevsky's classical memoir, Versuch einer natuerlichen Classification der fossilen Hufthiere, Osborn[552] writes:—"This work is a model union of the detailed study of form and function with theory and the working hypothesis. It regards the fossil not as a petrified skeleton, but as having belonged to a moving and feeding animal; every joint and facet has a meaning, each cusp a certain significance. Rising to the philosophy of the matter, it brings the mechanical perfection and adaptiveness of different types into relation with environment, with changes of herbage, with the introduction of grass. In this survey of competition it speculates upon the causes of the rise, spread, and extinction of each animal group. In other words, the fossil quadrupeds are treated biologically—so far as is possible in the obscurity of the past" (p. 8). The same high praise might with justice be accorded to the work of Cope on the functional evolution of the various types of limb-skeleton in Vertebrates, and on the evolution of the teeth as well as to the work of other American palaeontologists, including Osborn himself.

Osborn's law of "adaptive radiation," which links on to Darwin's law of divergence,[553] constitutes a brilliant vindication of the functional point of view. "According to this law each isolated region, if large and sufficiently varied in its topography, soil, climate, and vegetation, will give rise to a diversified mammalian fauna. From primitive central types branches will spring off in all directions, with teeth and prehensile organs modified to take advantage of every possible opportunity of securing food, and in adaptation of the body, limbs and feet to habitats of every kind, as shown in the diagram [on p. 363]. The larger the region and the more diverse the conditions, the greater the variety of mammals which will result.

"The most primitive mammals were probably small insectivorous or omnivorous forms, therefore with simple, short-crowned teeth, of slow-moving, ambulatory, terrestrial, or arboreal habit, and with short feet provided with claws. In seeking food and avoiding enemies in different habitats the limbs and feet radiate in four diverse directions; they either become fossorial or adapted to digging habits, natatorial or adapted to amphibious and finally to aquatic habits, cursorial or adapted to swift-moving, terrestrial progression, arboreal or adapted to tree life. Tree life leads, as its final stage, into

LIMBS AND FEET. Volant. / Fossorial. Arboreal. / Short-limbed, plantigrade, } Ambulatory pentadactyl, unguiculate } or Stem. } Terrestrial. / Natatorial. Cursorial Amphibious. Digitigrade. / Aquatic Unguligrade.

TEETH. Omnivorous. { Grass. { Fish. { Herb. Carnivorous { Flesh. Herbivorous { Shrub. { Carrion. / { Fruit. / { Root. / / Myrmecophagous. / / Dentition reduced. / / / / / / / / Stem: Insectivorous.

the parachute types of the flying squirrels and phalangers, or into the true flying types of the bats.... Similarly in the case of the teeth, insectivorous and omnivorous types appear to be more central and ancient than either the exclusively carnivorous or herbivorous types. Thus the extremes of carnivorous adaptation, as in the case of the cats, of omnivorous adaptation, as in the case of the bears, of herbivorous adaptation, as in the case of the horses, or myrmecophagous adaptation, as in the case of the anteaters, are all secondary" (loc. cit., pp. 23-4).

We have now reached the end of our historical survey of the problems of form. What the future course of morphology will be no one can say. But one may hazard the opinion that the present century will see a return to a simpler and more humble attitude towards the great and unsolved problems of animal form. Dogmatic materialism and dogmatic theories of evolution have in the past tended to blind us to the complexity and mysteriousness of vital phenomena. We need to look at living things with new eyes and a truer sympathy. We shall then see them as active, living, passionate beings like ourselves, and we shall seek in our morphology to interpret as far as may be their form in terms of their activity.

This is what Aristotle tried to do, and a succession of master-minds after him. We shall do well to get all the help from them we can.

[519] See E. B. Wilson's masterly book, The Cell in Development and Inheritance, New York and London, 1900.

[520] Q.J.M.S., xxvi. 1886.

[521] Wood's Holl Biological Lectures for 1893.

[522] Arch. f. Ent.-Mech., i., pp. 380-90, 1895.

[523] Beitraege zur Kritik der Darwinschen Lehre, Leipzig, 1898.

[524] See E. B. Wilson, "The Embryological Criterion of Homology," Wood's Holl Biological Lectures, Boston, pp. 101-24, 1895; Braem, Biol. Centrblt., xv., 1895; T. H. Morgan, Arch. f. Ent.-Mech., xviii.; J. W. Jenkinson, Mem. Manchester Lit. Phil. Soc., 1906, and Vertebrate Embryology, Oxford, 1913; A. Sedgwick, article "Embryology" in Ency. Brit., p. 318, vol. xi., 11th Ed. (1910).

[525] For a detailed treatment of this important point see the remarkable volume of E. Schulz (Petrograd), Prinzipien der rationellen vergleichenden Embryologie, Leipzig, 1910.

[526] "La Poecilogonie," Bull. Sci. France et Belgique, xxxix., pp. 153-87, 1905.

[527] Un probleme de l'evolution. La loi biogenetique fondamentale, Paris and Montpellier, 1908.

[528] Vergleichung des Entwickelungsgrades der Organe zu verschiedenen Entwickelungszeiten bei Wirbeltieren, Jena, 1891.

[529] Quoted by Keibel, Ergebn. Anat. Entwick., vii., p. 741.

[530] "Studien zur Entwickelungsgeschichte des Schweines," Schwalbe's Morphol. Arbeiten, iii., 1893, and v., 1895.

Normentafeln zur Entwickelungsgeschichte des Schweines, Jena, 1897.

"Das biogenetische Grundgesetz und die Cenogenese," Ergebn. Anat. Entw., vii., pp. 722-92, 1897.

"U. d. Entwickelungsgrad der Organe," Handb. vergl. exper. Entwick. der Wirbelthiere, iii., 3, pp. 131-48, 1906.

[531] "Beitraege zur Embryologie der Wiederkaeuer," Arch. Anat. Entw., 1889.

[532] "Die individ. Variation d. Wirbeltierembryo," Morph. Arbeit., v., 1895.

[533] "U. Variabilitaet u. Wachstum d. embryonalen Koerpers," Morph. Jahrb., xxiv., 1896.

[534] "Gastrulation u. Keimblaetterbildung der Emys lutaria taurica," Morph. Arbeit., i., 1891. "Kainogenese," Morph. Arbeit., vii., pp. 1-156, 1897, and also separately. Biomechanik, erschlossen aus dem Prinzipe der Organogenese, Jena, 1898.

[535] This law was foreshadowed by Reichert in 1837, when he wrote:—"We notice in our investigation of embryos of different animal forms that it is those organs, those systems, which in the fully developed individual are peculiarly perfect, that in their earliest rudiments and also throughout the whole course of their development appear with the most striking distinctness" (Mueller's Archiv, p. 135, 1837). See also his Entwick. Kopf. nackt. Amphib., p. 198, 1838. So, too, Rathke notes how the elongated shape of the snake appears even in very early embryonic stages (Entwick. Natter., p. 111, 1839).

[536] Quoted by Keibel (p. 790, 1897) from the Biomechanik.

[537] Die Zelle und die Gewebe, Jena, 1898, and the subsequent editions of this text-book, published under the title of Allgemeine Biologie. Die Entwickelung der Biologie im neunzehnten Jahrhundert, Jena, 1900, 2nd ed., 1908. "Ueber die Stellung der vergl. Entwickelungslehre zur vergl. Anatomie, zur Systematik und Descendenztheorie," Handb. vergl. exper. Entwickelungslehre der Wirbeltiere, iii., 3, pp. 149-80, Jena, 1906. (1906, b). Also in Pt. I. of Vol. I. (1906, a).

[538] An Essay on Classification, London, 1859.

[539] Unsere Koerperform, Leipzig, 1874.

[540] Q.J.M.S., xxxvi., pp. 35-52, 1894.

[541] Quoted by Hertwig. See also K. Goebel, "Die Grundprobleme der heutigen Pflanzenmorphologie," Biol. Centrbl., xxv., pp. 65-83, 1905.

[542] This is also emphasised by Fleischmann in his critical study of evolutionary morphology entitled Die Descendenztheorie, Leipzig, 1901.

[543] The same remark applies to the bulk of speculation as to the factors of evolution, with the exception of the contributions made to evolution theory by the palaeontologists by profession, such as Cope.

[544] Les Transformations du Monde animal, Paris, 1907.

[545] "Malacology versus Palaeoconchology," Proc. Malacological Soc., viii., pp. 66-83, 1908.

[546] Particularly by E. Perrier, "La Tachygenese," Ann. Sci. nat. (Zool.) (8), xvi., 1903.

[547] Monatsber. k. Akad. Wiss., Berlin, pp. 474-504, 1866.

[548] Geognost. u. Palaeont. Beitraege, ii., Heft 2, pp. 181-256, 1869.

[549] Abhand. k.k. Geol. Reichsanstalt, vii., Wien, 1875.

[550] The case for polyphyletism is very strongly put by G. Steinmann in his book, Die geologischen Grundlagen der Abstammungslehre, Leipzig, 1908.

[551] The steps in this chronological variation were termed by Waagen "mutations."

[552] The Age of Mammals in Europe, Asia, and North America, New York, 1910.

[553] Origin of Species, 6th ed., Chap. IV.



INDEX

ACTINOZOAN THEORY of Vertebrate Descent, 299-300

Adaptation as Conservative Principle— Cuvier, 39, 76

Adaptation, Ecological— Von Baer, 123 H. Milne-Edwards, 199 Lamarck, 221, 222, 223, 224, 227 Treviranus, 225 f.n. C. Darwin, 231-2, 235, 239 Haeckel, 248, 263 Gegenbaur, 263 V. O. Kowalevsky, 362 Osborn, 362-4

Adaptation, Ecological, and Classification— Bronn, 203

Adaptation of Parts. See "Correlation, Functional," and "Conditions of Existence"

Adaptive Radiation (Osborn), 362-4

Agassiz, A., 288 f.n., 295 On Coelom, 296

Agassiz, L.— Criticism of Vertebral Theory of Skull, 157 Membrane and Cartilage Bones, 164 Transcendentalism, 203 Classification, 203 f.n. Three-fold Parallelism, 230, 255 Influence on Darwin, 238 Specific Distinctness of Embryos, 353

Albertus Magnus, 17

Alcmaeon, 1

Aldrovandus, 18

Allman, 209

Analogy. See also Homology. Aristotle, 8-10 Owen, 108 Haeckel, 251 Gegenbaur, 266 Lankester, 267

Anaxagoras, 14

Anaximander, 14

Anaximenes, 1

Animal and Vegetative Lives— Aristotle, 16, 32 Buffon, 26-7 Bergson, 26 f.n. Cuvier, 26, 32 Bichat, 27-9 Oken, 94 K. G. Carus, 94 Von Baer, 116, 123, 131 Remak (Sensory and trophic layers), 210 Gegenbaur, 263

Annelid Theory of Vertebrate Descent, 274-85, 301

Archetype, Anatomical, 246, 302-3 E. Geoffroy, 54, 67 Owen, 104-7, 110 J. V. Carus, Huxley, 204 C. Darwin, 238 f.n.

Archetype, Anatomical, as Ancestral— C. Darwin, 235, 247 Haeckel, 251 Gegenbaur, 265 Sedgwick, 300 Criticism of this idea— O. Hertwig, 355-7

Archetype, Embryological, 168, 246, 302-3 Von Baer, 126, 132 Reichert, 139, 147, 149 Rathke, 151, 153 Huxley, 159-61

Archetype, Embryological, as Ancestral— C. Darwin, 233, 236-7 Haeckel, 254, 289-91 Gegenbaur, 266 O. and R. Hertwig, 298 Sedgwick, 300 A. Kowalevsky, 300

Arendt, 162

Aristotle, 2-16, 17, 345, 364 Historia Animalium, 2 De Partibus Animalium, 2, 9 Knowledge of Animals, 3, 4 Comparative Embryology, 4 Classification of Animals, 4-6 Unity of Plan, 6-7, 10 Homology and Analogy, 7-10 Teleology and Correlation, 10-12 Law of Compensation, 11 Division of Labour, 12 Degrees of Composition—homogeneous and heterogeneous parts, 12-14, 169 Law of Development (Von Baer), 14 Scale of Beings, 14-16 Functional attitude, 15-16, 197 Animal and Vegetative Lives, 16, 32

Ascidian Theory of Vertebrate Descent, 269-73, 304

Atomists, 16

Atomists, "Biological," 192-4

Audouin, V.— Unity of plan in Arthropods, 85-6 Law of Compensation, 86 Marine Zoology, 195

Autenrieth, 90, 96

Avicenna, 17

BABAK, E., 333

Baer, K. E. von, 113-32, 133, 251, 304, 345, 356 Founder of Embryology, 113 Entwickelungsgeschichte der Thiere, 114 Regulation of Development, 114, 350 Development as Differentiation, 115, 128 Germ-Layer Theory, 115-6, 118-119, 208-9, 296 Morphological Differentiation, 116-7 Histological Differentiation, 117-8 Tissues and Germ-Layers, 118 Double symmetrical Development, 118, 279 Criticism of Meckel-Serres Law, 120-3, 304 Theory of Types, 123-4, 289, 291 Law of Development, 124-6 Embryological Criterion, 126-8, 132, 138 Embryological Archetype, 126, 132 Types of Development, 127-8 Von Baer and Cuvier, 128-30 Functional attitude, 129 Relation to Transcendentalists, 129, 131 Criticism of Scale of Beings, 130 Vertebral Theory of Skull, 131, 142 Serial Homology, 131-2 Gill-slits, Gill-arches and Aortic arches, 135-6, 146 Membrane and Cartilage Bones, 162-3 Degrees of Composition, 172 Ova of Mammals, 175-6 Segmentation of Ovum, 186 Criticism of Evolution Theory, 229, 242 Influence on Darwin, 236, 238 Criticism of Darwinism, 242 Teleology and Correlation, 242 On Ascidians, 271

Baer's Law. See "Development, Von Baer's Law"

Bagge, 187

Balanoglossus Theory of Vertebrate Descent, 285-7

Balbiani, 330

Balfour, F. M., 247, 299 Annelid Theory, 282-4 Gastrulation and Gastraea Theory, 295 Mesoderm, 296 f.n. Coelom, 297

Barfurth, D., 330

Barry, M., 186, 188

Bateson, W.— Metamerism, Vegetative Repetition, 286 Balanoglossus Theory, 286-7 On Phylogenetic Speculation, 302

Beard, J., 285

Belon, 18

Beneden van, and Julin, 271, 285, 346

Bensley, A. B., 311 f.n.

Bergmann, 187

Bergson, H., 26 f.n., 341, 345

Bernard, Claude, 195, 314

Bert, P., 315

Bichat, X., 27-30, 118, 132, 169, 178, 263 Animal and Vegetative Lives, 27-9 "General Anatomy," 29-30 Vie propre of Tissues, 30

Biogenetic Law. See"Development, Haeckel's Law"

Bischoff, 138 Segmentation, 186, 188

Blainville, de, 96, 128, 141, 199 f.n.

Bojanus, 96, 97

Bonnet, C.— Scale of Beings, 22-3, 220, 227 Evolution, 215 Regeneration, 315

Bonnet, R., 350

Bonnier, G., on Albertus Magnus, 17

Born, G., 330

Boveri, T., 270 f.n., 333

Braem, 347 f.n.

Braun, A., 355

Breschet, 138, 173

Bronn, H. G., 200-3, 248 Naturphilosophie, 201 Functional attitude, 201-3 Geometry of Organism, 201, 249 Theory of Types, 202 Principle of Connections, 202 Intrinsic Laws of Evolution, 202 Division of Labour, 202 Ecological Adaptation and Classification, 203

Brown, R., 171

Bruch, C., 203 f.n.

Buechner, 194, 248

Buffon, 24-7, 336 Scale of Beings, 24, 215 Unity of Plan, 24 Evolution, 24-5, 214 Classification, 25-6 Animal and Vegetative Lives, 26-7 Homology and Analogy, 27

Burckhardt, R., 3 f.n., 268 f.n.

Burdin, 96

Burmeister, 249 f.n.

Butler, S., 226 f.n., 313, 335-42 Relation to Lamarck, 335-7 Psychological Vitalism, 336-41 Heredity and Memory, 337-41 The Two Stages of Development, 337-9 Consciousness and Habit, 337-9 Recapitulation Theory, 339-40 Teleology, 341

CABANIS, 215

Camper, P., 45, 46

Carter, 293 f.n.

Carus, J. V.— Criticism of Embryological Criterion, 167 Morphology and Physiology, 194 Vertebral Theory of Skull, 203 On Archetype, 204 Evolution, 230

Carus, K.G.— Law of Parallelism, 94, 249 Vertebral Theory, 96 Geometry of Skeleton, 98-100 Splanchnoskeleton, 98, 140

Causal Morphology, 312-3, 315-34

Cell-Theory— Schwann, 169, 173-86, 188 C. F. Wolff, 170 Schleiden, 170-2 Criticism of Schwann-Schleiden Theory, 185-8 Virchow, Leydig, 188

Cell-Theory and Germ-Layer Theory— Remak, 209-12

Cell-Theory as Disintegrative— Schwann, 180-5, 248 Vogt, 190-1 Virchow, 191 Haeckel, 248 Criticism of this idea— Reichert, 192-3, 194 J. V. Carus, 194 Sedgwick, Whitman, 346

Cell-Theory, Influence on Morphology, 190

Cenogenesis, 258-9, 323

Chabry, 331

Child, C. M., 333

Chun, C, 317, 332

Classification of Animals— Aristotle, 4-6 Rondeletius, Aldrovandus, Gesner, 18 Linnaeus, 22 Buffon, 25-6 Cuvier, 39-41 E. Geoffroy, 60 L. Agassiz, 203 f.n. Lamarck, 216-7, 227, 228

Classification and Ecological Adaptation (Bronn), 203

Classification as Genealogical— Buffon, 24-5 Lamarck, 218, 228 C. Darwin, 233, 234, 247 Haeckel, 250-1, 254 Criticism of this idea, 303, 304, O. Hertwig, 356

Classification, Phylogenetic— Haeckel's, 289-94

Claus, 259

Co-adaptation, 326 f.n.

Coelom— Remak, 211 A. Kowalevsky, 270, 295, 297 Haeckel, 291, 295, 296 Lankester, 291, 297

Coelom, Theory of, 295-301

Cohen, 189

Coiter, 18

Colucci, 346

Compensation, Law of— Aristotle, 11 Goethe, 49 E. Geoffroy, 72-3 Audouin, 86. German Transcendentalists, 100

Condillac, 215

Conditions of Existence, Principle of— Cuvier, 34, 75-6, 239 Gegenbaur, 263-4 Roux, 324, 326 Spencer, Weismann, 326 f.n. Disregard for— Lamarck, 226 C. Darwin, 232, 238-41 Haeckel, 248, 264

Conklin, 333

Connections, Principle of— Goethe, 47 E. Geoffroy, 53-4, 62-3, 71, 74, 261 Audouin, 85

Connections, Principle of—contd. German Transcendentalists, 100 J. F. Meckel, 101 Owen, 107-8 Bronn, 202 C. Darwin, 234-5 Gegenbaur, 261 Semper, 279 In Embryology, 168 Main Principle of Morphology, 246, 302

Convergence— Milne-Edwards, 199 I. Geoffroy St Hilaire, 199 f.n., 206 C. Darwin, 236 Friedmann, Willey, Vialleton, 306 f.n.

Convergence, Rejected by Evolutionary Morphologists, 305, 312 Hubrecht, 305-6

Cope, E. D., 342, 357 f.n., 361, 362

Correlation, Functional— Aristotle, 10-12 Cuvier, 35-8, 239, 241 E. Geoffroy, 77 Von Hartmann, 240-1 Radl, 240 f.n., 241 Von Baer, 242 Gegenbaur, 264 Disregarded by— C. Darwin, 235, 238-41 Haeckel, 248, 264

Coste, 134, 138, 176, 187

Crampton, 332

Cunningham, J. T., 284

Cuvier, 26, 31-44, 89, 196, 197, 199 f.n., 278, 345, 361 Functional attitude, 31-6, 65, 75-8, 200, 305 Animal and Vegetative Lives, 32 Degrees of Composition, 32-3 Teleology, 33-5 Functional Adaptedness, 33-5, 324 Principle of Conditions of Existence, 34, 75-6, 239 Correlation, 35-8, 239, 241 Metabolism, 38 Adaptation as Conservative Principle, 39, 76 Classification, 39-41 Principle of Subordination of Characters, 40 Criticism of Scale of Beings, 39-40, 130 Type Theory, 41, 124, 289, 291 Criticism of Evolution-Theory, 41-4, 129, 304 Variation, Limits of, 42 Palaeontological Succession, 43 Polemic with Geoffroy, 64-5, 74-8 Criticism of Vertebral Theory of Skull, 97-8 Influence on J. F. Meckel, 101 Criticism of Meckel-Serres Law, 129-30, 304 As Embryologist, 130 Criticism of Lamarck, 228

Cytology, 346

Cytoplasm of Egg, Organ-forming Stuffs, 332-3

DALL, 361

D'Alton, 113

Dareste, C., 315

Darwin, Charles, 78, 230-41, 271, 304, 307, 336, 362 Systematist and Field Naturalist, 230, 231 Palaeontological Succession, 231 Ecological Adaptation, 231-2, 235, 239 Species Problem, 231 Functional Adaptation, Disregard for, 232, 238-41 Classification as genealogical, 233, 234, 247 Unity of Plan due to Community of Descent, 233, 234-5, 239, 247 Embryological Archetype as ancestral, 233, 236-7 Rejects Meckel-Serres Law, 233, 236 Interpretation of Vestigial Organs, 233, 237 Organism as Historical Being, 233, 308 Rejects Scale of Beings, 234 Homology, 234-5, 247 Principle of Connections, 234-5 Anatomical Archetype as ancestral, 235, 247 Von Baer's Law interpreted phylogenetically, 236-7 Modifications inherited at corresponding age, 237 Monophyletism and Polyphyletism, 238 Causes of Success, 238, 241

Darwin, Erasmus, 214, 226 f.n., 229, 336

Darwin, Sir Francis, 344

Daubenton, 26

Degrees of Composition— Aristotle, 12-14, 169 Glisson, 19 Malpighi, 20 Bichat, 29-30 Cuvier, 32-3, Dujardin, 169, 188 Von Baer, 172 Effect of Invention of Microscope, 20 Relation to Cell-Theory, 169

Delage, 333

Delage and Herouard, 273 f.n.

Delpino, 345

Demaillet, 44

Democritus, 16

Deperet, C, 357 On Cuvier, 43 Absence of intermediary forms in Palaeontology, 358 Phyletic series and Polyphyletism, 360-1

Development, Von Baer's Law— Aristotle, 14 Von Baer, 124-6 Prevost and Dumas, 125 f.n. Reichert, 149-50, 351 f.n. Milne-Edwards, 205-8 Lereboullet, 206-8 Criticised by— Agassiz, 352-3 His, 353 Sedgwick, 353 O. Hertwig, 354 Phylogenetic Interpretation of— Darwin, 236-7 Gegenbaur, 266 Relation to Haeckel's Law, 254, 256, 257

Development, Biogenetic Law (Haeckel)— Haeckel, 251, 253-9, 291-4 F. Mueller, 252-3, 254, 257 Gegenbaur, 262 Roux, 319 Butler, 339-40 Orr, 342 Criticism of— Vialleton, 348 Oppel, 348-9 Keibel, 349-50 Mehnert, 350-2 O. Hertwig, 352, 354-5 His, 353 Relation to Laws of Meckel-Serres and Von Baer, 254, 256, 257, 303, 309 Relation to Heredity and Development, 312-3 Influence of Causal Morphology, 347-8 Palaeontological Evidence for, 359

Development, Meckel-Serres Law— Harvey, 18 Hunter, 22 E. Geoffroy, 69-70, 72 Serres, 80-3, 94, 203-4, 205-6 Kielmeyer, Autenrieth, Oken, 90

Development, Meckel-Serres Law-contd. Tiedemann, 91 J. F. Meckel, 91-3 K. G. Carus, 94 Criticism of— Von Baer, 120-3, 304 Cuvier, 129-30, 304 Milne-Edwards, 205 Lereboullet, 206-8 C. Darwin, 233, 236 Analogy with Biogenetic Law, 254-7, 262, 303, 304, 309

Development, Meckel-Serres Law, Theory of Three-fold Parallelism— L. Agassiz, 230, 255 Tiedemann, Vogt, 255 f.n. Haeckel, 254-5

Development, The two periods of— Roux, 320-4, 325, 327, 335 Butler, 337-9

Diogenes of Apollonia, 1

Disintegration. See "Cell-Theory," and "Materialistic Attitude"

Division of Labour, Principle of— Aristotle, 12 Milne-Edwards, 197-8 Bronn, 202 Gegenbaur, 264

Dohrn, A., 269, 274-8 Annelid Theory of Vertebrate Descent, 274-7, 303 Principle of Function-Change, 276-8, 307 Functional Attitude, 277-8, 307 Formal Attitude, 306

Doellinger, I., 113, 157

Dollo, 311

Donne, 173

D'Orbigny, 43

Driesch, H., 242, 331, 332, 333, 334, 345, 346-7

Duges, A., 86-8, 100, 134, 142, 146 Unity of Plan, 87 Polyzoic conception of Organism, 87-8 Membrane and Cartilage Bones, 163

Dujardin, 169, 188

Dumas. See Prevost and Dumas

Dumeril, 96

Dumortier, 173

Dutrochet, 99 f.n., 130, 134

Duverney, 19

EAR-OSSICLES, Homology of— E. Geoffroy, 56 Spix, 100 Rathke, 141, 150 Reichert, 144-7

Echelle des etres. See "Scale of Beings."

Ehlers, 284

Eisig, H., 284, 285

Embryology, Comparative, Early Workers— Aristotle, 4, 113 Fabricius, Harvey, 18, 113 Malpighi, 20, 113 Oken and Kieser, 90, 113 Haller, C. F. Wolff, J. F. Meckel, Tiedemann, 113

Embryology, Experimental, 317, 318, 330-3

Embryological Archetype. See "Archetype, Embryological"

Embryological Criterion of Homology, 133-168, 347 Goethe, 49 E. Geoffroy, 72, 110 Cuvier, 75, 110, 130 Owen, 110-1 Von Baer, 126-8, 132, 138 Rathke, 138, 140-1 J. Mueller, 138 Reichert, 138-9, 144-7, 163 Vogt, 156-7 Huxley, 158-9, 166 Koelliker, 165-6 Criticised by— Owen, J. V. Carus, 167

Empedocles, 1, 15

Engramm (Semon), 343

Entwicklungsgesetz. See "Evolution, Intrinsic Laws of"

Entwicklungsmechanik, 315

Erasistratus, 17

Evolution Theory— Lucretius, 16 Buffon, 24-5, 214 Cuvier's criticism, 41-4, 129, 304 E. Geoffroy, 66-9, 73, 228 J. F. Meckel, 92-3, 215, 228 Leibniz, 213 Kant, 213-4 Erasmus Darwin, 214, 229 C. Bonnet, Oken, Robinet, Treviranus, 215 Tiedemann, 215, 255 f.n. Lamarck, 215-29 Von Baer, 229, 242 I. Geoffroy St Hilaire, J. V. Carus, 230 Charles Darwin, 230-41 Von Hartmann, 240-1, 244, 356 Koelliker, 243 Owen, 244 Milne-Edwards, 244-5 Haeckel, 250-9 Gegenbaur, 265 The Organism as an Historical Being, 308-13 C. Darwin, 233, 308 Haeckel, 252, 257 Sedgwick, 308 Roux, 313, 322-4 Butler, 313, 336-41

Evolution-Theory, Influence on Morphology, 302-13

Evolution, Intrinsic Laws of, 241 J. F. Meckel, 93 Bronn, 202 Von Baer, 229, 242, 356 Koelliker, Naegeei, 243, 356 Owen, 244 Von Hartmann, 244, 356 Milne-Edwards, 244-5 O. Hertwig, 354-5, 356-7 Wigand, 356 Deperet, 361

FABRICIUS, 18, 113

Fallopius, 18

Fischel, 346, 350

Fischer, 328

Fleischmann, 357 f.n.

Flourens, 46, 315

Fontana, 172

Forbes, E., 196

Formal Attitude, 246, 305 Goethe, 49 E. Geoffroy, 62-3, 71, 75-8, 305 Haeckel, 249, 257, 260 Gegenbaur, 261, 263 Semper, 279 Adopted by Evolutionary Morphologists, 302-8, 311-2, 314 Hubrecht, 305-6 Dohrn, 306

France, R., 345

Friedmann, 306 f.n.

Fuld, 333

Functional Adaptation, 316-7, 318, 320-9, 333, 344, 351

Functional Attitude— Aristotle, 15-6, 197 Bichat, 27-9 Cuvier, 31-6, 65, 75-8, 200, 305 Goethe, 49-50 J. F. Meckel, 101 Owen, 109, 110, 111 Von Baer, 129 Milne-Edwards, 195, 197-200 J. Mueller, Reichert, 200 Bronn, 201-3 Lamarck, 222-6, 307, 335 Gegenbaur, 260, 263-4 Dohrn, 277-8, 307 Roux, 320-9, 335 Houssay, 333 Butler, 336-41 G. Wolff, 346 Driesch, 346-7 Giard, 347 E. Schulz, 347 f.n. Keibel, 349-50 Mehnert, 350-1 American Palaeontologists, 361, 362 Ruetimeyer, 361 V. O. Kowalevsky, 361-2 Osborn, 362-4

Function-Change, Principle of— Dohrn, 276-8, 306, 307 Eisig, 284

Fuerbringer, M., 282 f.n., 284, 323 f.n.

GALEN, 17

Gastraea Theory, 269, 288-95, 298, 299-3O1, 303

Gastrula, Discovery of, 288

Gaupp, E., 310 f.n.

Gegenbaur, C, 247, 260-7, 271, 285, 286, 288 f.n. Division of Egg-nucleus, 188 Functional Attitude, 260, 263-4 Formal Attitude, 261, 263 Principle of Connections, 261 Embryology and Comparative Anatomy, 261-2, 263 Biogenetic and Meckel-Serres Laws, 262 Homology, 261, 263, 265, 266-7 Adaptation and Correlation, 263-4 Archetype as ancestral, 263 f.n, 265 On Phylogenetic Speculation, 265-6 Embryological Archetype, 266 Membrane and Cartilage Bones, 309, 310

Gemmill, J. F., 285 f.n., 312 f.n.

Geoffroy, Etienne, St Hilaire, 40, 52-78, 141 Unity of Plan, 52-65, 70 ff., as conservative, 75, 78 Principle of Connections, 53-4, 62-3, 71, 74, 261 Unity of Composition, 54, 70-1, 75-6, 200, 305 Archetype, 54, 67 Metastasis, 55-6, 59, 74 Opercular Bones, 56 Unity of Composition of Sternum, 57-60 Classification, 60 Vertebrates and Articulates, 60-4, 274, 278-9, 303 Formal Attitude, 62-3, 65, 71, 75-8, 305 Cephalopods and Vertebrates, 64-5 Scale of Beings, 64 Polemic with Cuvier, 64-5, 74-8 Evolution, 66-9, 73, 228 Biogenetic Law, 69 Teratology, 69, 315 Meckel-Serres Law, 70, 72 Criteria of Homology, 71, 72, 110 Law of Compensation, 72-3 Criticism of his Principles, 74 Relation to German Transcendentalists, 89, 100-1 Vertebral Theory of Skull, 96, 97 Influence on Darwin, 234-5, 238

Geoffroy, Isidore, St Hilaire, 65 f.n., 199 f.n., 230

Geometry of the Organism, 33 K. G. Carus, 98-100, 249 Bronn, 201, 249 Haeckel, J. Mueller, Burmeister, G. Jaeger, 249

Germinal Vesicle (Egg-nucleus), 175-7, 188, 291 f.n.

Germ-Layer Theory— Von Baer, 115-6, 118-9, 208-9, 296 Pander, 119-20, 209 C. F. Wolff, 119-20 Rathke, 136, 208 Lereboullet, Bischoff, 208 Huxley, 208, 289 Remak, 209-12, 296

Germ-Layers and Gastraea Theory— Haeckel, 289-95 Lankester, Balfour, 295

Germ-Layer Theory, Influence of Causal Morphology on, 347

Gesner, 18

Giard, A.— On Ascidian Theory, 271-3 Adaptive Homology, 273 Poecilogeny, 347-8

Glisson, F., 19

Gluge, 173

Goebel, K., 356 f.n.

Goethe, 45-51, 65, 89, 250 Unity of Plan, 45-7, 51 Homology, 47 Principle of Connections, 47 Formal and Functional Attitudes, 48-50 Teleology, 48 Metamorphosis of Plants, 48 Repetition of parts, 48-9 Vertebral Theory of Skull, 49, 96, 97 Law of Compensation, 49 Embryological Criterion, 49 Organisms as Nature's Works of Art, 50

Goette, 259

Graaf, von, 175

Grew, N., 169

Gruber, 330

HAECKEL, Ernst, 247-60, 271, 314, 342, 353, 357 His sources, 248-50 Materialism, 248, 250 On Teleology, Heredity and Adaptation, 248, 263 Correlation, Disregard for, 248, 264 Geometry of the Organism (Promorphology), 249 Repetition of Parts (Tectology), 249-50 Classification as Genealogical, 250-1, 254 Archetype as ancestral, 251 Homology and Analogy, 251 Biogenetic Law, 251, 253-9, 291-4 Three-fold parallelism, 254-5 Scale of Beings, 255, 256-7 Organism as an Historical Being, 257 Prussianism, 257 Palingenesis, 258 Cenogenesis, 258-9 Heterotopy, Heterochrony, 259 Gastraea Theory, 269, 288-95 Phylogenetic Classification, 289-94 Criticism of Theory of Types, Monophyletism, 289, 291 Gastraea Theory and Biogenetic Law, 291-4 Primary stages of Ontogeny and Phylogeny, 291-3 Coelom, 291, 295, 296 Experimental Embryology, 317

Haller, 113

Harting, 284 f.n.

Hartmann, E. von— On Darwin's conception of correlation, 240-1 Evolution, 244, 356

Hartog, M., 344

Harvey, 18, 113

Hatschek, 270 f.n., 299

Helmholtz, H. von, 195

Henle, 172

Hensen, V., 209 f.n.

Herbst, C., 333

Herder, 46

Heredity and Memory, 336-44

Hering, E., 341-2

"Heritage" Characters, 309, 322

Herlitzka, 332

Herophilus, 17

Hertwig, O., 163, 330, 331, 346 On C. F. Wolff, 119 Fertilisation, 291 f.n. Membrane and Cartilage Bones, 309-10 Biogenetic Law, 352, 354-5 Von Baer's Law, 354 Intrinsic Laws of Evolution, 354-5, 356-7 Homology not necessarily Homogeny, 355-7 Unity of Plan not necessarily due to Community of Descent, 355-7 On Phylogenetic Speculation, 356

Hertwig, O. and R.— Coelom Theory, 297-8 Nervous System of Coelentera, 299

Heterochrony, 259, 348, 349-52

Heterogeneous Generation (Koelliker), 243

Heterotopy, 259

Hilgendorf, 359

Hill, 311

Hippocratic Treatises, 2

His, W., 206 f.n., 209 f.n. Causal Morphology, 316 Cytoplasm of Egg, Organ-forming Stuffs, 333 Specific Distinctness of Embryos, 353

Histological Differentiation (von Baer), 117-8

Histology. See also "Cell-Theory" Malpighi, 20 Stensen, 21 Bichat, 29-30, 169, 178 Von Baer, 117-8 Schwann, 178 Remak, 209-12

Hofer, B., 330

Hofmeister, 185

Homogeny, 267, 303, 355

Homology, 168, 303, 355-7. See also "Connections, Principle of," and "Embryological Criterion" Aristotle, 7-10 Belon, 18 Buffon, 27 Goethe, 47 E. Geoffroy, 53, 71 Serres, 80 Owen, 107-9 Lamarck, 227 C. Darwin, 234-5, 247 Haeckel, 251 Gegenbaur, 261, 263, 265, 266-7 Giard, 273 Semper, 279 O. Hertwig, 355-7 Braun, 355

Homology, Genetic Definition of— Gegenbaur, 266 Lankester, 267 O. Hertwig's criticism, 355-7

Homoplasy, 267

Hooke, R., 20, 169

Houssay, F., 19 f.n., 333

Hubrecht, A. A. W., 284, 295 f.n., 301, 305-6

Hunter, J., 22, 315

Huschke, 134-5, 136, 141, 146

Huxley, T. H., 157, 238, 247 On Rathke, 154 f.n. Embryological Criterion, 158-9, 166 Embryological Archetype, 159-61 Criticism of Vertebral Theory of Skull, 161-2 Membrane and Cartilage Bones, 166-7 On Archetype, 204 Germ-Layer Theory, 208, 289 Criticism of Three-fold Parallelism, 230 f.n. Coelom, 297 Ancestry of Marsupials, 311

Hyatt, A., 359, 361

INSTINCT and Morphogenesis, Analogy of, vi., 307, 312 Lamarck, 220, 226

JACOBSON , 164

Jaeger, G., 249 f.n.

Jardin des Plantes, Paris, 19

Jenkinson, J. W., 347 f.n. On His, 316

Jones, Wharton, 138, 176

Julin, C., 271, 285

Jussieu, de, 40

KANT, I.— Teleology, 35, 213, 242 Unity of Plan, 46, 213-4 Evolution, 213-4

Keibel, F., 348, 349-50

Kerkring, 131

Kielmeyer, 89, 90, 96

Kieser, 90

Kleinenberg, N., 277

Kohlbrugge, J., 44 f.n., 65 f.n.

Koelliker, A.— On C. F. Wolff, 119 Vertebral Theory of Skull, 157 Membrane and Cartilage Bones, 164-6, 310 Embryological Criterion, 165-6 Cell-division, 187 Intrinsic Laws of Evolution, 243, 356 Saltatory Variation, 243

Kowalevsky, A., 269-71, 284, 285, 299, 300 Development of Amphioxus, 270 Ascidians, 270-1 Coelom, 270, 295, 297 Gastrula, 288

Kowalevsky, V. O., 361-2

Krause, 176

Kupffer, 271

LACAZE-DUTHIERS, H. de, 203 f.n., 315-6 On Ascidians, 271, 273

Lamarck, 44, 66, 78, 215-29 Relation to Buffon, 215 Scale of Beings, 215-8, 220-1, 227-8 As Evolutionary, 218, 220 Classification, 216-7, 227, 228 Species Problem, 216, 227 Materialism, 218-9, 222-3, 225-6 Psychological Vitalism, 219, 220-6, 307, 335 Sentiment interieur, 219-20, 222-3, 225 Ecological Adaptation, 221, 222, 223, 224, 227 Laws of Evolution, 221-5 Transmission of Acquired Characters, 221-2, 224 Subtle Fluids, 222 Use and Disuse, 223-4 Independence of Current Thought, 226-7 Homology and Analogy, 227 Reception of his Theory, 228-9 Lamarck and Butler, 335-7

Lang, A., 301

Lankester, Sir E. Ray, 247 Homology, Homogeny, Homoplasy, and Analogy, 267 Balanoglossus Theory of Vertebrate Descent, 287 Germ-Layer Theory and Phylogenetic Classification, 291 Planula Theory, 295 On Coelom Theory, 296-7, 299 f.n.

Latreille, 86, 100

Laurencet, 64

Lavocat, 203 f.n.

Leeuenhoek, 20, 21, 169

Leibniz, 23, 213, 343

Lereboullet— Von Baer's Law, 206-8 Germ-layer Theory, 208 Gastrula, 288 f.n.

Leucippus, 16

Leuckart, 193 f.n., 194, 297

Levy, O., 333

Leydig, 187, 188, 275 f.n., 285

Linnaeus, 22

Loeb, J., 333, 347

Loi de Balancement. See "Compensation, Law of"

Loven, 186, 196

Lucretius, 16 On the Soul, 222 f.n.

Ludwig, 193, 194, 314

Lyell, Sir C., 228 f.n.

Lyonnet, 22

MACBRIDE, E. W., 287 f.n.

M'Kendrick, J.— On Fontana, 172

Mackenzie, W., 345

Malpighi, M., 20-1, 113, 169

Marine Zoology, Rise of, 195-6

Materialistic Attitude, 246-7, 345, 364 Schwann, 180-5 Vogt, 190-1 Virchow, 191 Ludwig, 193 Materialistic Physiology, 193-4, 314-5, 347 Lamarck, 218-9, 222-3, 225-6 The Darwinians, 241, 308 Haeckel, 248, 250 Roux, 315, 317, 318-9, 329 Semon, 343 Rignano, 344 Loeb, 347 Criticism of this attitude— Reichert, 192-3

Meckel, D. A., 95

Meckel, J. F., 113 Meckel-Serres Law, 91-3 Evolution, 92-3, 215, 228 Teratology, 93-4 Repetition of Parts, 95 Vertebral Theory of Skull, 96 Eclecticism, 101

Meckel's Cartilage, 141, 145

Meckel-Serres Law. See "Development, Meckel-Serres Law"

Mehnert, E., 348, 350-2

Membrane and Cartilage Bones, 162-7, 309-10

Memory and Heredity, 336-44

Mendelism, 346

Mesenchyme, 298

Mesoderm, 209-11, 296, 297, 298

Metabolism— Cuvier, 38 Schwann, 182-5 Roux, 324, 329

Metamerism, 94, 95, 100, 109, 131-2, 266-7, 274-5, 279, 282, 286, 299, 301

Metamorphosis of Plants, 48, 235

Metastasis, Principle of— E. Geoffroy, 55-6, 59, 74 Owen, 106

Metschnikoff, E., 278 f.n., 285, 288 Criticism of Ascidian Theory, 271 Coelom, 295, 296, 297

Meyen, 170, 185

Meyer, E., 284

Meyranx, 64

Microscope, Invention of, 19

Milne-Edwards, H., 12, 86, 238 Marine Zoology, 195 Functional Attitude, 195, 197-200 Unity of Plan, 197 Division of Labour, 197-8 Ecological Adaptation, Convergence, 199 Von Baer's Law, Polemic with Serres, 204-8 Evolution, 244-5

Mirbel, 170, 171

Mivart, St G., 277

Mohl, von, 170, 185

Moldenhawer, 170

Moleschott, 194

Moquin-Tandon, A., 87

Morgan, T. H., 317 f.n., 332, 333, 347 f.n.

Mosaic Theory of Development, 330-3

Mueller, F., Biogenetic Law, 252-3, 254, 257

Mueller, H., 166

Mueller, J., 136, 209 f.n., 260, 285, 309, 345 Embryological Criterion, 138 Vertebral Theory of Skull, 142-4, 154, 157 On Reichert, 150 Cell Theory, 172-3 Division of Egg-nucleus, 188 Vitalism, 192 Marine Zoology, 196 Functional Attitude, 200

Mutations (Waagen), 361 f.n.

NAEGELI, 185, 243 f.n., 356

Naturphilosophie. See "Philosophy of Nature"

Nesbitt, R., 162

Neumayr, 357, 360

Nussbaum, M., 330

OKEN, L., 89, 113, 131, 134, 149 Meckel-Serres Law, 90-1 Teratology, 91 Repetition of Parts, 94-5 Serial Homology, 95-6, 100 Vertebral Theory, 96, 97, 98 On Geoffroy, 100 Influence on Serres, 205 Evolution, 215

Ollier, 315

Oppel, A., 318 f.n., 324 f.n., 327, 348-9

Orr, H. F., 342

Osborn, H. F., 214 f.n., 361 On V. O. Kowalevsky, 362 Functional Attitude, 362-4 Law of Adaptive Radiation, 362-4

Owen, R., 97, 102-12, 204 Eclecticism, 102 Vertebral Theory of Skeleton, 103-7 Archetype of Vertebrate Skeleton, 104-7, 110 Vertebral Theory of Skull, 104-6 Metastasis, 106 Principle of Connections, 107-8 Anatomy and Embryology, 108 Homology and Analogy, 108 Classes of Homology, 108-9, 266 Functional Attitude, 109, 110, 111 Embryological Criterion, 110, 167 Homological and Teleological Compoundedness, 110-1 Vegetative Repetition of Parts, 111, 286 Unity of Plan as Conservative Principle, 112 Influence on Darwin, 234, 235, 238 Evolution, 244

PACKARD, 361

Palaeontological Record, 357-61 Absence of connecting forms, 357-9 Biogenetic Law, 359 Phyletic Series, 359-61

Palaeontological Succession— Cuvier, 43 E. Geoffroy, 67 L. Agassiz, 230, 255 C. Darwin, 231 Milne-Edwards, 245 Tiedemann, 255 f.n.

Paley, W., 341

Palingenesis (Haeckel), 258, 323

Pander, 113, 119-20, 133, 208, 209

Parallelism, Theory of. See "Development, Meckel-Serres Law" Three-fold. See "Development, Meckel-Serres Law"

Paris Museum of Natural History, 19, 89, 101

Paul, 360

Pauly, A., 345

Perrault, C., 19

Perrier, E., 88, 359 f.n.

Pflueger, E., 317, 330

Philipeaux, 315

"Philosophy of Nature," 89, 94, 98, 203, 248

Phyletic Series, 359-61

Physiology, Separation from Morphology, 194, 247, 260, 314

Physiology of Development, 315

Planula Theory (Lankester), 295

Plato, 15

Pockels, 138

Poecilogeny (Giard), 347-8

Poli, 175

Polyphyletism— Darwin, 238 Von Baer, 242, 356 Koelliker, Wigand, Naegeli, 356 Deperet, 360-1 Steinmann, 360 f.n.

Polyzoic Conception of Organism— Duges, 87 Perrier, 88

Prevost and Dumas, 125 f.n., 134, 175, 186

Promorphology (Haeckel), 249

Protoplasm, 169, 188-9

Purkinje, 172, 173, 175, 176, 189

QUATREFAGES, A. de, 172, 195-6

RADL, E., on Goethe, 48 Correlation, 240 f.n., 241 On Darwin's Critics, 242 f.n. On Cuvier's Critics, 278 f.n.

Rathke, H., 133, 136-7, 174, 194, 269, 351 f.n. Discovery of Gill-slits in Pig and Chick, 134 Discovery of Gill-slits in Man, 135 Germ-Layer Theory, 136, 208 Embryological Criterion, 138, 140-1 Homologies of Gill-arches, 139-41, 146, 150 Development of Skull, 141, 150-4 Vertebral Theory of Skull, 141, 154-6 Embryological Archetype, 151, 153 Membrane and Cartilage Bones, 163, 166

Rauber, A., 330

Reaumur, 22, 315

Recapitulation Theory. See "Development, Biogenetic Law"

Regeneration, 315, 318, 333, 346

Regulatory Processes in Development, 114, 319, 333, 346-7, 350

Reichert, C. B., Embryological Criterion, 138-9, 144-7, 163 Archetype, 139, 147, 149 Homologies of Gill-arches and Ear-ossicles, 144-7 Vertebral Theory of Skull, 147-9, 157 Von Baer's Law, 149-50, 351 f.n. Membrane and Cartilage Bones, 163, 165, 166, 310 Criticism of "Biological Atomists," 192-3, 194 Functional Attitude, 193, 200

Remak, R., 118, 288 f.n. On Vertebrae, 157 Cell Theory, 173, 187-8, 209 Microscopical Technique, 209 f.n. Germ-Layer Theory, 209-12, 296 Cells, Tissues and Germ-Layers, 209-12 Mesoderm, 209-11 Coelom, 211, 296

Repetition of Parts within the Organism, Theory of. See also "Vertebral Theory of Skull" Goethe, 48-9 Duges, 87-8 Oken, 94-5 J. F. Meckel, D. A. Meckel, 95 Haeckel (Tectology), 249-50

Reymond, E. du Bois, 194, 314

Rignano, E., 343-4

Robinet, 23, 215

Rondeletius, 18

Rosenhof, Roesel von, 22

Roux, W., 313, 315-29, 344, 351 Entwicklungsmechanik, 315, 317-8 Materialistic Attitude, 315, 317, 318-9, 329 Functional Adaptation, 316-7, 318, 320-9, 333 Experimental Embryology, 317, 318, 330-1 Simple and Complex Components, 318-20 Functional Definition of Life, 320 Functional Attitude, 320-9, 335 The Two Periods of Development, 320-4, 325, 327, 335 Mosaic Theory of Development, 323, 330-1 Metabolism, 324, 329 Structure, Functional and Non-functional, 324-6 Functional Unity of Organism, 326 Functional Adaptation of Blood-vessels, 326-9 Form as manifestation of Activity, 329

Ruini, C., 18

Rusconi, 133-4, 186

Ruetimeyer, L., 361

Ryder, 361

SACHS, J. von, 170

St Ange, M., 146

Salensky, 259

Saltatory Variation— E. Geoffroy, 78 Von Baer, 242 Koelliker, 243 Owen, 244

Sarcode, 169

Sars, M., 186, 196

Savigny, J. C., 83-5, 100, 137, 271

Scale of Beings, 89, 206, 214-5 Aristotle, 14-6 Anaximander, Anaxagoras, 14 Empedocles, Plato, 15 Albertus Magnus, 17 C. Bonnet, 22-3 Robinet, 23 Buffon, 24 E. Geoffroy, 64 Lamarck, 215-8, 220-1, 227-8 As Evolutionary, 218, 220 Haeckel, 256-7 Criticism of this idea— Cuvier, 39-40, 130 Von Baer, 130 Milne-Edwards, 205 Lereboullet, 207 Darwin, 234 Haeckel, 255 Relation to Evolution-Theory, 214-5

Schepelmann, 333

Schleiden, 170-2

Schmieden, 328

Schults, C. H., 173

Schultze, Max, 189

Schultze, O., 331

Schulz, E., 347 f.n.

Schwann, Theodor, 169, 173-86, 248 Physiological Standpoint, 173, 179, 180, 182 Development of Cells, 174-5, 179-80 Cellular Nature of Ovum, 175-7 Development of Tissues from Cells, 177-8 Histology, 178 Materialism and Teleology, 180-3, 185 Cell-metabolism, 182-5 Cells as organic Crystals, 184-5

Sedgwick, A., 347 f.n. Actinozoan Theory of Vertebrate Descent, 299-300 Metamerism, 299 Embryological Archetype, 300 Organism as Historical Being, 308 Cell-Theory, 346 Von Baer's Law, 353

Segmentation of Ovum, 186-8

Seiler, 138

Selection, Natural and Artificial, 307 f.n.

Self-Differentiation (Roux), 319, 320-1, 322, 323, 324, 327

Self-Regulation (Roux), 319

Semon, R., 342-3

Semper, C., 259, 269, 278-82, 284, 286 Annelid Theory, 274, 278-82 Metamerism, 274, 279, 282 Follower of Geoffroy, 278 Unity of Plan and Composition, 279, 303 Principle of Connections, 279 Formal Attitude, 279

Sentiment interieur (Lamarck), 219-20, 222-3, 225

Serial Homology. See "Metamerism"

Serres, E., 79-83, 91, 100, 205-6, 257 f.n. Criteria of Homology, 80 Law of parallelism, 80-3, 94, 203-4, 205-6 Law of Multiple Formation, 80-1 Unity of Plan, 83, 205, 206 Teratology, 83 Meckel's Cartilage, 145 f.n. Transcendentalism, 205-6 Concrescence Theory, 206 f.n.

Severino, 18

Sharpey, 162, 176

Siebold, von, 186

Skull, Development of, 139-62. See also "Vertebral Theory"

Spallanzani, 315

Species-Problem— Cuvier, 42 Lamarck, 216, 227 Darwin, 231

Spencer, H., 326 f.n.

Spengel, 285, 287

Spinoza, 343

Spix, 96, 97, 100, 141

Stannius, 165

Steenstrup, 309

Steinmann, G., 357, 360 f.n.

Stensen (Steno), 21

Swammerdam, 20, 21-2

TACHYGENESIS, 359

Technique, Microscopical, 209 f.n., 268

Tectology (Haeckel), 249

Teleology— Aristotle, 10 Cuvier, 33-5 Kant, 35, 213, 242 Von Baer, 242 Owen, Von Hartmann, 244 Butler, 341 G. Wolff, Driesch, 346 Criticism of— Goethe, 48 Schwann, 180-2 The Darwinians, 241 Haeckel, 248 Evolutionary Morphologists, 308

Teratology, 69, 83, 91, 93, 315

Thienemann, 23 f.n.

Thompson, D'Arcy W., 2 f.n.

Thomson, A., 176

Thomson, J. Arthur, 215 f.n.

Tiedemann, 91, 113, 215, 255 f.n.

Tissues and Germ-Layers, 118, 209-12

Transcendental Anatomy, Relation to Evolutionary Morphology, 302-8, 312

Transcendentalism, French and German Schools, 89, 100

Trembley, 22, 315

Treviranus, 141, 170, 215, 225 f.n.

Turpin, 173

Types, Theory of (Cuvier and Von Baer)— Cuvier, 41, 124, 289, 291 Von Baer, 123-4, 289, 291 Bronn, 202 Lereboullet, 207

Types, Theory of (Cuvier and Von Baer)—contd. Criticised by— E. Geoffroy, 60 Haeckel, 289, 291 Lankester, 291

Type-Theory and Evolution, 304

UNGER, 185

Unity of Composition, Principle of, Geoffroy, 54, 70-2, 75-6, 200, 305

Unity of Plan, 88, 241, 278-9, 303, 312. See also "Archetype" Aristotle, 6-7, 10 Belon, Severino, 18 Perrault, 19 Robinet, 23 Buffon, 24 Cuvier, 41 Goethe, 45-7, 51 Vicq D'Azyr, 45 Camper, 45, 46 Herder, 46 Kant, 46, 213-4 E. Geoffroy, 52-65, 70 ff. Serres, 83, 205, 206 Savigny, 83 Audouin, 85-6 Latreille, 86 Duges, 86-7 J. F. Meckel, 101 Milne-Edwards, 197 Semper, 279 Haeckel, 289, 291 Lankester, 291

Unity of Plan as due to Community of Descent— Darwin, 233, 234-5, 239, 247 Haeckel, 250-1 Gegenbaur, 263 f.n., 265 Criticism of this idea— O. Hertwig, 355-7

Unity of Plan as Conservative Principle— E. Geoffroy, 75, 78 Owen, 112 Gegenbaur, 263-4 Evolutionary Morphologists, 307

VALENTIN, 138, 173, 176

Variation, Limits of, Cuvier, 42

Vegetative Repetition of Parts— Owen, 111, 286 Bateson, 286

Velpeau, 138

Vertebral Theory of Skull, 49, 96-9, 104-6, 131, 141-4, 147-9, 154-7, 161-2, 165, 203, 235, 310 f.n.

Vertebrate Descent, 269-87, 299-301, 304

Verworn, M., 330

Vesalius, 18

Vestigial Organs, 233, 237, 309, 312

Vialleton, L., 306 f.n., 348

Vicq d'Azyr, 45, 95

Virchow, R., 188, 191

Vitalism, Psychological— Lamarck, 219, 220-6, 307, 335 Butler, 336-41 Orr, Cope, 342 Ward, 343 Delpino, France, Pauly, A. Wagner, Mackenzie, 345

Vogt, C.— Criticism of Vertebral Theory, 156-7 Capillaries, 179 Segmentation, 186 Materialistic Attitude, 190-1 Threefold Parallelism, 255 f.n.

WAAGEN, 359, 361 f.n.

Wagner, A., 345

Wagner, R., 176

Ward, J., 343

Weber, 138

Weismann, A., 240, 323, 326 f.n., 330-1, 343

Werneck, 173

Whitman, C. O., 346

Wigand, A., 242 f.n., 356

Willey, A., 273 f.n., 306 f.n.

Williamson, 309

Willis, 19

Wilson, E. B., 331, 332-3, 346 f.n., 347 f.n.

Wolff, C. F., 113 Germ-layer Theory, 119-20 Cells, 170

Wolff, G., 346-7

Woodward, B. B., 358

Wotton, E., 17

ZELENY, 333

Zittel, K. von, 357, 358

Zoja, 331

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THERAPEUTICS OF THE CIRCULATION. By Sir T. Lauder Brunton, Bart., M.D., LL.D., F.R.C.P., F.R.S., Consulting Physician to St Bartholomew's Hospital. New and Revised Edition. With Illustrations. 5s. net.

In this new edition so much matter has been added that the book has been practically re-written. It is intended to supplement, and not to replace, the usual text books dealing with circulation.

THE PREVENTION OF MALARIA. By Sir Ronald Ross, K.C.B., F.R.S., etc. With Contributions by twenty of the Leading Experts. With Illustrations. Demy 8vo. 21s. net.

"A thoroughly sound and comprehensive treatise; Sir Ronald Ross and his colleagues have turned out work worthy of their high reputations. The student of malaria in all respects will find in this work the most complete exposition of the subject in medical literature."—Lancet.

THE HOUSE-FLY: Disease Carrier. An Account of its dangerous activities and of the means of destroying it. By Leland O. Howard, Ph.D. With numerous Illustrations. 6s. net.

In this book the Chief of the U.S. Bureau of Entomology sets forth complete information about the fly.

After describing the nature of the common house-fly, its habits and methods of breeding, he proves his case against it as a carrier of disease, and goes on to what will be the most interesting section to most readers—that on remedies and preventive measures. A special point is made or the possibilities of action by communities, with suggestions as to organisation, publicity, interesting the children, and the work of Boards of Health.

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WORKS BY EDWARD HALFORD ROSS, M.R.C.S. (Eng.), L.R.C.P. (Lond.).

Of the John Howard McFadden Researches; the Lister Institute of Preventive Medicine, London; and sometime Health Officer, Port Said, the Suez Canal District and Cairo.

THE REDUCTION OF DOMESTIC MOSQUITOS. Instructions for the use of Municipalities, Town Councils, Health Officers, Sanitary Inspectors, and Residents in Warm Climates. Demy 8vo. 5s. net.

THE REDUCTION OF DOMESTIC FLIES. With Illustrations. Demy 8vo. 5s. net.

LONDON: JOHN MURRAY, ALBEMARLE STREET, W.

THE END